The present invention relates generally to the art of filtration, and more particularly relates to rotary vacuum drum filters of the type employing endless flexible filter belts and used in both commercial processes and municipal sewage water reclamation systems for the separation of large amounts of solids from suspension in a liquid slurry.
While rotary vacuum drum filters of the type employing an endless flexible filter belt have an established place in filtration installations, they have until the present invention had their shortcomings or disadvantages. In the typical rotary vacuum drum filter arrangement much of the drum periphery is needed for the formation of a cake, leaving only about 120.degree. of the drum periphery for dewatering and drying. This small amount of drying area severely limited the dryness which could be obtained and made the adaptation of (1) additional operations such as cake washing and (2) external drying aids such as forced air or radiant heat extremely difficult.
Also, in the typical rotary vacuum drum filter arrangement, the drum is suspended in a slurry tank so that the cake is formed on the lower part of the drum. Such an arrangement has the disadvantage of requiring greater vacuum values since the cake must be formed against the force of gravity. Furthermore, heavier particles will not attach themselves to the cake, but will settle to the bottom of the slurry tank in spite of any turbulance in the slurry. Settling particles will eventually require cleaning of the slurry tank which means an interruption in the so-called continuous process.
The present invention is directed to a solution of the abovementioned shortcomings with conventional rotary vacuum drum filter arrangements.